Non-aqueous electrolyte secondary batteries, as typified by lithium ion secondary batteries, are characterized by having high energy density, and thus are widely used as power sources for portable devices, including, for example, mobile phones and notebook personal computers. The capacity of lithium ion secondary batteries is likely to increase further as the performance of portable devices is enhanced. Accordingly, the research and development for further increasing the energy density is underway.
Meanwhile, with the recent enhancement of the performance of non-aqueous electrolyte secondary batteries, non-aqueous electrolyte secondary batteries have begun to be used as power sources other than those for portable devices. For example, non-aqueous electrolyte secondary batteries have begun to be used also as power sources for automobiles and motorcycles, and power sources for moving objects such as robots. In the case of using non-aqueous electrolyte secondary batteries as power sources for automobiles and motorcycles, and power sources for moving objects such as robots, it is necessary to further increase the capacity.
One example of the methods for increasing the capacity of non-aqueous electrolyte secondary batteries is a method involving increasing the thickness of an electrode material mixture layer. However, simply increasing the thickness of the electrode material mixture layer may lead to a capacity decrease during high-output charging and discharging. One of the reasons for this seems to be that there will be an increased amount of the active material whose distance from the current collector increases as the thickness of the electrode material mixture layer is increased, and thus the conductivity within the electrode is reduced.
Meanwhile, for example, Patent Document 1 proposes a method involving coating a positive electrode active material with a silane compound and a conductivity enhancing agent as a method for increasing the conductivity within the electrode.